Pneumatic balancing system for tiltable bodies



April 7, 1953 R. A. POAGE 2,633,811

PNEUMATIC BALANCING SYSTEM FOR TILTABLE BODIES Filed Nov. 10, 1948 5 Sheets-Sheet l Attorney April 7, 1953 R. AQPOAGE 2,633,811

PNEUMATIC BALANCING SYSTEM FOR TILTABLE BODIES Filed Nov. 10, 1948 5 Sheets-Sheet 2 Inventor fiafierf 24 P259 Attorney April 7, 1953 R. A. POAGE 2,633,811

PNEUMATIC BALANCING SYSTEM FOR TILTABLE BODIES Filed Nov. 10, 1948 5 Sheets-Sheet s l I 93 70 23 43 I .5. fit

:2 a?! \I 2? 66 95 k\ 49 53 )2 I .9. I 5 U as s By 1% L i? Hf Ap 7, 1953 R. A. POAGE PNEUMATIC BALANCING sysmm FOR TILTABLE BODIES Filed Nov. 10, 1948 5 Sheets-Shet 5 Inventor By )1. M

Attorney Patented Apr. 7, 1953 PNEUMATIC BALANCING SYSTEM FOR TILTAELE BODIES 7 Robert A. Poage, Hannibal, Mo. Application November 10, 1948, Serial No. 59,271

12 Claims.

This invention relates to a novel pneumatic balancing and supporting system for tiltable bodies and particularly to a novel actuating means for a control unit thereof.

Another object of the invention is to provide a pneumatic balancing system which is under pneumatic pressure throughout and including a control or directing unit which is interposed i the system and responsive to any and all forces resulting in an unbalanced load on the support lug means of the system for returning the load to a balanced position.

"Another and particularly important object of the invention is to provide a balancing system which isresponsive to such forces as gravity, centrifugal force, air resistance, wind and sway.

' Another object of the invention is to provide a balancing system including pneumatic supporting cushions of relatively large size capable of functioning under a relatively'low pressure to afiord'a soft cushioning support for a load carryingbody.

' "A further object ofthe invention is to. provide a novel pump for the system requirin no valves and which functions to produce "a fluctuatin pressure in a portion of the system for cooperation with thedirecting' unit of the system-for transferring pressure to an overloaded side of the system from the other side of the system which is bearing less than its share of the load for returning the load to a balanced position and which will function without afiecting the load supporting portions of the system when a balanced condition of the system exists.

'i Other objects of the invention are to provide a' pneumatic balancing system which is affected solely by differentials of pressure in th support ing means thereof, which is provided with a directing or control unit having valves which are actuated by fluctuation of pressure in a portion of the system produced by the pumping unit only when an unbalanced condition exists between the individual supporting means of the system, and inwhich the compressible gas, such as air, with which the system is inflated constitutes both the cushioning and the energy medium thereof.

4 Afurth'er object of "the invention is to provide a. system wherein said cushioning and energy me diumfis sealed'within the system and under press'ure throughout all portions of the system and due'to its" compressibility permits the necessary fluctuation of pressurein a portion of the system produced by the pumping unit.

\ -Numerous other objects and advantages of the invention .will hereinafter become more fully apparent from the following description of the drawings, illustrating presently preferred embodiments thereof, and wherein: m

Figure 1 is an end elevational View partly in cross section illustrating a simple embodiment ofthe invention applied to the truck of a railroad:

car for supporting an end of the car body thereon and illustrating the system in a balanced condition;

Figure 2 is a view similar to and with the preponderance of the load on the right-hand side thereof;.

Figure 3 is a view similar to Figure 1 but showing the system unbalanced in the opposite direction resultin from a preponderance of the loa leaning to the left;

Figure 4 is a view similar to Figure lillustrating a slightly modified form of the railroad truck and another, preferred form of actuating means for the pumping unit of the system, taken substantially along a plane as indicated by the line 44 of Figure 18;

Figure 5 is an enlarged fragmentary vertical sectional view taken substantially along a plane as indicated by the line 5 5 of Figure 4;-

Figure 6 is a side elevational view, partly invertical section illustrating another form of pump actuating means for the pneumatic system;

Figure '7 is an enlarged side elevational View partly in section of the pump, constituting a, part of the system;

Figure 8 is a central vertical sectional view of the directing unit or control unit of the system as it will appear when a balanced load condition exists, as in Figure l;

Figure 9 is a view similar to Figure 8 but showing the directing unit as it will appear when an unbalanced load condition exists on the system as in Figure 2;

Figure 10 is a view similar to Figure 8 but showingthe directing unit as it will appear when an unbalanced load condition exists on the system as illustrated in Figure 3;

Figure 11 is a side elevational View, partly in vertical section, of one of the cushionin supi porting members of the system;

Figure 12 is a fragmentary verticallsectional view of a portion thereof on an enlarged scale; I

Figure 13 is a view similar to Figure 12 but illustrating a slightly modified form of the, cushioning supporting member; s

Figure 14 is a view similar to Figure 11 showing another form of the cushioningpsubporting m m e I I Figure 1 but illustrating the system in an unbalanced condition Figure 15 is a top plan view thereof taken substantially along a plane as indicated by the line |5|5 of Figure 14;

Figure 16 is a fragmentary vertical sectional view of another form of the supporting cushioning member;

Figure 17 is an end view in elevation of the directing unit taken substantially along a plane as indicated by the line of Figure 8;

Figure 18 is a horizontal sectional view taken substantially along a plane as indicated by the line |8| 8 of Figure 4, and

Figure 19 is a side elevational View taken substantially along a plane as indicated by the line |3-|9 of Figure 4.

Referring more specifically to the drawings and first with reference to Figures 1, 2 and 3, to illustrate a preferred application and use ofthe pneumatic balancing system for tiltable bodies, the numeral 20 designates generally a truck of a railroad car provided with flanged wheels 2| shown engaging a pairof rails 22. The truck-26 is illustrated as including an undercarriage 23 and a bolster 24 the vertical sides of which are vertically slotted as seen at 25 to accommodate pins 26 which-are disposed longitudinally of the truck on the undercarriage-23 for mounting the bolster 24 for vertical reciprocating movement and lateral rocking movement relatively to the undercarriagefl. A crossbeam of a railway car body-asseen at -27, is supported on the upper surfaceof the bolster 24 and is swivellyconnected to the truck 20 by a vertical kingpin 28 which rises from the center of the bolster 2d and turnably engages a countersunk opening 29 of the body crossbeam 21. It is to be understood that the structure previously described is conventional and has been disclosed merely to illustrate one application of the pneumatic balancing system one form of which, designated generally 33, is shown applied to the truck 20 in Figures 1, 2 and 3.

The pneumatic balancing system 39 is illustrated as including a bellows-type pump 3| composed generally of a compression chamber 32 and a bellows 33 having an openend fastened to and communicating with the chamber 32. The pump 3| corresponds to the pump 3 la as illustrated in Figure 7 in all respects except that the compression chamber 32 has an inlet and outlet nipple 34 located in its outer side whereas the inlet and outlet nipple 34a of the pump 3|a is disposed in a portion of the periphery of the compression chamber 32a. The pump 3| may be mounted on designated generally 43 and which are disposed in laterally spaced relationship relatively to the longitudinal axis of the truck and between corresponding portions of the undercarriage 23 and bolster 24 for yieldably supporting the lateral ends of the bolster 24 on the undercarriage 23. Each of the supporting members includes a bellowsd l having a closed lower end which is secured to and supported o'na base 45. The base 45 is provided with a depending rounded projection 45 which seats in an upwardly opening re- "cess 41 in the undercarriage 23 for supporting the base 45 for oscillating movement in all di rections upon said undercarriage.

Each oi the supporting members 43 is closed "except for a connection at its upper end with a conduit 38 which communicates with the interior thereof and which leads therefrom to one side of the bolster 23 by means of any suitable bracket, I

not shown, extending from the compression chamber 32 and secured to the bolster 24. A plate or head 35 is fastened to the opposite, closed end of the bellows 33 and has a rod 35 proj cting therefrom in a direction away from the pump 3| and which terminates in an elongated loop '3'! which is disposed transversely to the axis of said rod for loosely engaging a crankpin 38 which is mounted eccentrically on a wheel orfpulley 33 which is journalled on a stub-shaft "43 project'- iiig from a portion of the bolster 24. The wheel or pulley 39 may be revolved in any manner for causing the eccentric pin 3t to reciprocate the rod 36 and bellows 33 for producing a fluctuation of pressure within the compression chamber 32, as by means of an electric motor 4| suitably supported on the bolster 24 and having a drive shaft provided with a pulley 42 which is connected by abeltfl to the pulley 39. v V

The balancing system 30 includes a pair "of corresponding cushioning supporting members, each a directing or control unit, designated generally 49. For clarity in subsequently describing the operation "of the system 30, the left-hand supporting member will hereinafter be referred to generally as the supporting member 33a and the conduit thereof will be described as the conduit 48a.

The directing unit 49 is formed of corresponding end sections 52! and 5| having detachably connected flanged inn-=r ends secured together by fastenings 52 whichalso clamp the peripheral portions of a diaphragm 53 forminga partition between the sectionstfl and 5lasclearly illustrated in Figures 8, 9 and 10. The sections "50 and 5| are provided with complementary internally threaded ports 54 and 54a, respectively for receiving the opposite ends of the conduits I8 and 48a and said sections 50 and "5| are provided with lower internally threaded ports '55 and 5511, respectively for accommodating complementary ends of branch conduits 5E and 51 which join with a main conduit 58 which is connected to the nipple 34 and accordingly in communication with the pump 3|.

The section 5|] of the directing unit 4'9 is provided with alower outletport 59 and an upper inlet port 69, adjacent its outer end, each of which ports communicates with the port '55. The section 5| is provided with complemefitaryports 59a and im each of which communicates with the port 55a. Correspondingplates 6| are suitably secured toopposite sides of the centralj'por tion of the diaphragm 53 and each of s'aidj'plates has a head 6-2 projecting perpendicularly therefrom forming an abutment for one end of an-expansion coiled spring '63the opposite end of which seats against a valve 64. Each of the inlet'iports 63 and 60a is normally closed by one of the valves '64 and said heads 32 and valves 64 are provided with stems 35 whichp'roje'ct from adja cent sides thereof for supporting the (and pottions of the springs 63. The valves 64 are'dis posed on the internal sides of the inlet ports 60 and 33m and the outlet ports '53 and 59a arenor mally closed by externally disposed, outwardly opening valves '65 having stems 61 extending iii-'- wa'rdly through said ports and wh'ich are pro* vided on their inner ends with eyes each of which is adapted to engage an end of a centred-'- tile coiled spring 6'3. The opposite, adjacent'ehds of the springs '68 are connected to eyesfifi on-the plates 3| and function to normally urge the valves 63 inwardly for "closing the outlet ports 53 and 59a. I

Assuming that the system as illustrated in Fig-- ures l, 2 and '3, including th'epump 3|,thes'up-i porting cushioning members 43 and 4311, 'the'directing 49 and the comma connecting said parts is filled with a compressible gas such as air and assuming that the motor 4| is operating to revolve the pulley wheel 39 for actuating the pump 3|, if the load is in a balanced position as illustrated in Figure 1 the directing unit 49 will be in the position of Figure 8 so that the compressible medium will merelybe compressed and permitted to expand as the pump 3| is 0perated, as to the portion thereof disposed within said pump and in the conduit 53, since the pressure of the compressed medium in the supporting members 43 and 43a will be in communication with the directing unit on each side of the diaphragm 53 so that there will be no tendency for the diaphragm to be displaced in either direction from its position of Figure 8 so that the pressure exertedby the springs 63 and 68 will be substantially equal and sufiicient with the pressure from the supporting members 43 and 43a to maintain the valves 64 and 66 in their closed positions of Figure ,8. 1 However, this will not prevent the pump 3! from operating since the medium can be compressed therein, as previously described. The pump bellows 33 is similar in construction to the bellows 44 of the supporting members and the pressure 7 in the compression chamber 32 thereof rises and falls in relationship to the movement of the butt plate 35 toward and away from said compression chamber 32, respectively. The stroke of the butt plate 35 is sufficient to fluctuate the pressure within the chamber 32 to an extent substantially greater than the differential of pressures encountered in the cushioning supporting members 43 and 4311 or, in other words, the pressure in the chamber 32 rises higher than the pressure in the overloaded cushioning member 43 or 430; and falls to a point lower than the pressure in the other, underloaded cushioning member, when the load is not equally balanced, as illustrated in Figures 2 and 3. For example, assuming that the load supported by the cushioning members is such as to require a fifty pound pressure per square inch therein, when a balanced condition exists, whereas a maximum unbalanced condition of said cushioning members would result in a pressure of forty pounds per square inch in the underloaded cushioning member and sixty pounds per squareinoh in the overloaded cushioning member. With this diiferential of pressure of twenty pounds per square inch maximum established, the pump 3! is constructed capable of causing a thirty pound pressure per square inch fluctuation in the compression chamber 32, ranging between thirty-five pounds and sixty-five pounds. With the load in balance as illustrated in Figure l, the directingunit 43 as illustrated in Figure 8 is likewise in balance and with the diaphragm centered and with the pairs of valves 64 and 66 equally spring loaded. The springs of said valves have sufficient strength to prevent the valves from being opened by the aforementioned fluctuation of pressure in the compression chamber 32 so that no air passes through the directing unit 49.

With the load unbalanced and heavier on the right, as illustrated in Figures 2 and'9, the diaphragm 53 is displaced to the left by the additional pressure from the conduit 48 so that the pairs of valves are thus unequally spring loaded. This will cause the tension-on the valve spring 63 of the directing unit section 50 to be decreased as the'ftension of the other valve spring 63 is increased so that the left-hand valve 64 remains closed while the right-hand valve 64 will be openedby the pressure rise in the compression.

chamber 32 to permit air to pass into the directing unitsection 50 through the port 60 thereof for increasing the pressure in the cushioning member 43. Likewise, the tension of the spring 68 of the directing unit section 50 is increased to hold the valve 66 thereof in a closed position while the pressure of the other spring 68 is decreased so that the left-hand valve 66, constituting a part of the directing unit section 5|, may open to release the pressure therefrom and to diminish the pressure in the other, left-hand cushioning member 43a, when the pressure in the pump chamber 32 falls to its minimum, thus effecting a' transfer of pressure from the underloaded cushioning member 43a to the overload cushioning member 43 for the purpose of return ing the load to its balanced position, as illustrated in Figure 1.

It will be readily apparent from the foregoing that the operation just previously described will be reversed when the cushioning member 43a is overloaded, as illustrated in Figure 3.

Furthermore, since the pump 31 is operating constantly, it will function to return the load to a balanced position whether the unbalancing of the load results from gravity due to an unequal distribution of pay load, centrifugal force resulting from the vehicle moving around a turn, air resistance caused by passing near an object located close to one side of the vehicle, the lateral force of wind against one side of the vehicle body or sway due to undulation of the track.

The form of the invention previously described and as illustrated in Figures 1, 2 and 3, constitutes a simple embodiment of the pneumatic balancing system, a preferred form of which is illustrated in Figures 4 and 5, wherein the truck 20a differs from the truck 20 only in that the forward and rear depending sides of the bolster 25!! are provided with substantially triangularshaped openings. Likewise, the cross beam 21a is swivelly supported on the bolster 24a in the same manner as the cross beam 27 on bolster 24.

The pneumatic balancing system of Figures 4 and 5 designated generally 300; includes a' pump am having a compression chamber 32a and a bellows 33a. The pump 31a is disposed substantially in a vertical position with the outer, closed side of the compression chamber 32a being secured in any suitable mannerv to the underside of the upper part of the bolster 24a. The pump 31a differs from the pump 3| in that the inlet and outlet fitting 34a thereof extends through the side wall of the compression chamber 32a. The butt plate 35a of the pump 3m corresponds with the butt plate 35 but in lieu of being provided with the rod 36 is provided with an apertured ear 36a which depends therefrom. The directing unit 49a of the system 3011 corresponds in all internal detail with the directing unit 49 and is supported on the underside of the bolster 24a by an external bracket 10 which is bolted to the under surface of the uper part of the bolster 23a. The directing unit 139a is connected by the fitting 34a to the pump 31a by conduits 53a, 51a and 58a, in the same manner that the pump 3! is connected to the directing unit 49. As the cushioning members of the system 30a are identical with those of the system 30, these cushioning members bear the same reference characters 43and 43a and are connected by corresponding conduits 48 and 48ato the directing unit 49a.

The pneumatic balancing system 30:; diifers from thesystern 30 primarily in i1}? means 91 whereas inthe form of Figures 4 and 5 the conduits 48- and 48a as indicated in dotted lines in Figure 4 extend upwardly through diagonal openings, not shown, in the top portion of the bolster 24a. The plate 95 is provided with an upwardly opening threaded recess I (ll which may be utilized to receive a bolt, not shown, extending downwardly through the bolster for detachably fastening the cushioning member 43 or 43a thereto. 7

Figure 13 illustrates a slightly modified form of the cushioning member 43 or 43a and wherein the bellows 44 thereof is provided with an inner lining I02 of rubber or the like.

Figures 14 and 15 illustrate another modificationof the cushioning supporting member and which is additionallyprovided with an internal snubber; unit, designated generally I03 which is in communication with the nipple I 00 and which includes a housing I04 secured by a fastening 105 to the underside of the plate 95 and which is closed at its upper end by said plate. The housingIM is provided at its lower end' with a continuous inturned flange I06 defining arelatively largev opening Ill'i which is normally closed by a plate 198 except for a small port I99 in said plate. The plate I08 normally rests on the flange I06. The plate I98 is smaller than the internal cross section of the housing I04 and is limited in its movement away from the flange I06 by the stop pins H0. This rebound snubber unit I63 will permit the ends of the bellows M to yield rapidly toward one another since the plate I08 will then be unseated as indicated in dotted lines in Figure 14 so that the air can enter the housing I 04 around said plate I08. However, upon rebound or expansion of the bellows M, the plate I OBi will assume its full line, closed position so that the compressed medium can only escape from the housing .IM into the bellows 44 through the breather port I 09.

I Figure 16 illustrates another form of the cushioning supporting member and which is provided with -a central dividing plate II I) having a peripheral clamping portion IL! for engaging an intermediate portion of the bellows 44 for dividing the chamber thereof into upper and lower compartments. The upper compartment thereof communicates with the nipple I00, not shown, and the lower compartment may be provided with a nipple H2 which'extends downwardly through the table 45 and which could be connected with the same or a different source of a compressible medium or with an hydraulic medium if desired.

Figure 18 shows the truck 20a as it would appear'from above and equipped with the pneumatic system as illustrated in Figures 4' and 5 and designated generally 3| a and Figure 19 is a side elevational view of the truck and showing a portion of a vehicle body IIA supported thereby on the body crossbeam 21 which is swivelly connectedto the bolster 24a.

j Various modifications and changes are contemplated and may obviously 'be' resorted to, without departing from the spirit or scope of the invention as hereinafter defined by the appended claims.

I claim as my invention: 4 l; A vehicle balancing system closed throughout and containing a compressible medium for maintaining the system under pressure throughout, comprising laterally spaced cushioning supporting members adapted to be interposed between an undercarriage and a bolster of a vehicle body supporting truck and equally spaced from bolster above the undercarriage, said cushioning supporting members each including an inflatable chamber capable of being compressed between the bolster and undercarriage in response to lateral tilt of the bolster; a sealed conduit system including said cushioning supporting members containing a compressed medium under pressure, driven means connected to the conduit system for pro ducing a fluctuation of pressure in said conduit system, and a directing unit interposed in said conduit system between said fluctuation producing means and the cushioning supporting mem bers and provided with spring loaded valvesto prevent flow of the compressed means through said directing unit when the pressure of a load on the cushioning supporting members is substantially balanced, said valves being actuated in response to an unbalanced loadcondition on'the cushioning supporting members to cause the com-' pressed medium to flow past the directingunit as the pressure fluctuates in the system toward an overloaded supporting member and away from an underloaded supporting member.

2. A vehicle balancing system, as inclaim 1; said cushioning supporting members each including a sealed bellows-type flexible chamber inflated by the compressible medium to provide a yield able support for the bolster, and a snubber unit contained within said chamber for restricting the flow of the compressible medium thereto for regulating the expansion of the chamber.

' 3. A vehicle balancing system as inclaim 1",}

said cushioning supporting members each including a sealed bellows-type flexible chamber inflatedby the compressible medium to. provide a yieldable support for the bolster, and a partition dividing said chamber into separate upper and lower compartments.

4. A vehicle balancing unit comprising a conduit system closed throughout and containing a compressible medium for maintaining the system under pressure throughout, laterally spaced cushioning supporting members connected to and forming a part of the conduit system and adapted to be interposed between an undercarriage and a bolster of a vehicle body supporting truck and equally spaced from the sides of the'truck for yieldably supporting the bolster above the undercarriage, said cushioning supporting members each including an inflatable chamber capable of being compressed between the bolster and undercarriage in response to lateral tilt of the bolster driven means forproducing a fluctuation of pres; sure in said system, and a directing unit interposed in said system between said fluctuation producing means and the cushioning supporting members and provided with spring loaded valves to prevent flow of the compressed medium through said directing unit when the pressure of a load on'the cushioning supporting members is sub stantially balanced, said valves being actuated in response to an unbalanced load condition on the cushioning supporting members to cause the compressed medium to flow past the directing unit as the pressure fluctuates in the systemtoward an overloaded supporting member and away from an underloaded supporting member, said driven means for fluctuating the pressure in the eastern including a pump having a compression chamber forming one end thereof and a bellows constituting the opposite end of the pump and defining a chamber of variable size in communi cation with the compression chamber.

mestides of the truck for m b upporting the x A vehicle balancing unit comprising a con.

i 1- duit system closed throughout and containing a compressible medium for maintaining the system under pressure'throughout, laterally spaced cushioning supporting members connected to and forming a part of'thecond'uit' system and adapted to be interposed between an undercarriage and a bolster of a vehicle body supporting truck and equally spaced from the sides of the truck for yielda'bly supporting the bolster above the undercarriage, said cushioning supporting members each including an inflatable chamber capable of being compressed between thebolster and underc'arriage" in response to lateral tiltof the bolster; di tvel'i' means forproducing a. fluctuation of pressure in said. system, and a directing. unit interposed ins'ai'd.systembetween said fluctuation producing means and the cushion supporting members and: provided with spring loaded valves to preveiit fioiv of the compressed medium through said directing unit when the pressure of a load on the? cushioning supporting members is substan: tially balanced, sa-idvalves being actuated in response to an unbalanced load condition. onthe cushioning supporting members to cause thecompressed medium toilow past the directing unit as the pressure fluctuates in the system. toward an overloaded supporting member and: away from an underloaded supporting member, said directing unit comprising an elongated housing, a resilient diaphragm dividing. said housing into corresponding end sections, each of saidend sections being in communication with the portion of the system leading from the directing unit to said driven fluctuation producing means, each of said cushioning supporting members being in direct communication with a different one of said housing sections; a pair of valves for closing ports of the housing sections communicating with the portion of. the system leading tosaid driven fluctuation producing, means, springs normally holding said valves in closed positions and connected to said diaphragm, and said diaphragm. being displaced toward one section of the. housing by an excess load onthe cushioning supporting. member connected to the other section of the housing for varying, the: tension of said springs to cause one of the valvesto open when the pressure is increased in the system by the fluctuation producing' means to permit the compressed medium to pass to saidaforementioned, overloaded cushion- F ing supporting member, and another. valve of. said directing unit being. opened when the fluctuating pressure in. the" system diminishes to permit the compressed medium. from the: other, underloaded cushioning supporting. member to ,flow pastthe directing. unit toward said fluctuation producing means.

6; A vehicle balancing unit comprising a conduit system closed throughout and containing a compressible medium under pressure, laterally spaced oppositely positioned cushioning supporting members connected to and forming a part of the conduit system and adapted to be interposed between laterally spaced portions of an undercarriage and bolster of a vehicle truck for yieldably supporting the. bolster above the undercarriage and adapted to provide a yieldable support between the undercarriage and a portion of a load carrying body supported on the bolster, said cushioning supporting members being laterally spaced relatively to the body and truck and substantially equally spaced from the sides thereof, said cushioning supporting members each including an inflated chamber capable of being compressed in response to lateral tilt of the vehicle body; a pump in the conduit system, means for continuouslydriving the pump when the vehicle is' in motion, a directing unit interposed the conduit system between the pumpand the cushioning supporting members; said directing unit havin -ports connectin each cushioningsupport ing'member with the pump, valves for closing said ports whenthe pressure in the cushioni'ngmemhers is substantially equalized to prevent the compressed medium from flowing past thedi recting unit, springs fornormally retaining the valves in closed positions; the operationof the pump causing'a fluctuation of the pressure in the portion of the conduit system between the pumpand directing unit, and an unbalanced load condition on the body acting to increase the pressure on an overloaded cushioning supporting member to vary" the tension of thespri'ngs for causing one of the valves to open when the pressure is increased by the pump to supply the compressed medium to the, overloaded cushioning supporting, member and for permitting another of the valves. to open when the pressure adjacent the pump diminishes to allow the, compressed medium to pass from an underloaded cushioning supporting member past the directing unit toward the pump.

7. A vehicle balancing system as in claim 6', pump including a compression chamber and a bellows communicating therewith atone of its ends, a driven eccentric; constituting the means for continuously driving the pump, connected to the opposite end of said bellows forreciprocating said last mentioned end toward, and away from said compression chamber:

8. A vehicle balancing system as-in claimfi, said pump including a compression chamber and a bellows communicating therewith at one. of its ends, a driven eccentric, constituting the means for continuously driving the. pump, connected to the opposite end of said bellows for reciprocating said last mentioned end toward and away from said compression chamber, and a prime mover connected to and driving the eccentric.

9. A. vehicle balancing system as in. claim 6; said pump including a compression chamber and a bellows communicating therewith at one of its ends, a driven eccentric, constituting the means for continuously driving the pump, connected to the opposite end of said bellows for reciprocating said last mentioned end toward and away from said compression chamber, said. driven eccentric being adapted to be fixed. to. a wheelaxle of the truck.

l0. A. vehiclev balancing system as. in claimfi, Said pump including a reciprocating bellows, said means for continuously driving the pump includmg a lever pivotally supported on the bolster. and pivotally connected to an end of the bellows, said lever having a cam slot, a bell crank pivotally supported on the bolster and having, one end pivotally connected to the undercarriage. and. its opposite end engaging said cam slotfor. rocking the lever to reciprocate the pump bellows when said bolster is moved relatively to the undercarriage in response to vibrations. of, the truck.

11. In a closed balancing system containing a compressible medium, cushioning supporting members adapted to be interposed between anonyielding supporting surface and a superimposed load for yieldably supporting the load on said surface, each of said cushioning supporting members having an inflatable chamber forming apart of the closed system, a, continuously driven pump connected to the system for causing a fluctuat of pressure therein, and a. directing unit interposed in the system between the pump and said cushioning supporting members, said directing unit having spring loaded valves responsive to the fluctuations in pressure in the system when an unbalanced load condition exists on the cushioning supporting members whereby upon upward fluctuation of the pressure in the system between the pump and directing unit the compressed medium will pass through the directing unit to an overloaded cushioning supporting member and on a downward fluctuation of pressure in the system the compressed medium will pass from an underloaded cushioning supporting member through the directing unit toward the pump.

12. A balancing system as in"claim 11, said directing unit comprising an elongated housing, a flexible diaphragm dividing said housing into corresponding ends, each of said housing ends being in direct communication with one of said cushioning supporting members and being connected to a portion of the system leading to the pump, each of said housing sections having a, pair of said valves interposed between the diaphragm and the portion of the system leading to the pump and normally disposed in closed positions, springs for said valves connected to said diaphragm for REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 779,858 Lillie g.. Jan. 10, 1905 1,008,290 Verge Nov. 7, 1911 1,303,808 Loraille May 6, 1919 2,088,487 Schoepf et al July 27, 1937 2,095,677 Schoepf et al Oct. 12, 1987 2,192,865 Kuhn Mar. 5, 1940 2,208,537 Brown July 16, 1940 2,469,962 Gouirand May 10, 1949 2,474,471 Dolan June 28, 1949 

